Process for preparing a monoalkyl aromatic

ABSTRACT

AN IMPROVEMENT IN A PROCESS WHEREIN A FIRST COMPOUND IS CONVERTED TO A SECOND COMPOUND IN AN ESSENTIALLY IRREVERSIBLE REACTION OR TO THE SECOND COMPOUND AND TO A THIRD COMPOUND IN ESSENTIALLY IRREVERSIBLE REACTIONS, THE SECOND COMPOUND AND THE THIRD COMPOUND ARE CONVERTIBLE TO EACH OTHER IN EQUILIBRIUM-LIMITED REACTIONS AND THE THIRD COMPOUND IS INITIALLY PRESENT IN THE REACTION ZONE IN AN AMOUNT GREATER THAN THE AMOUNT THAT WOULD BE PRESENT AT EQUILIBRIUM, WHICH INVOLVES INTRODUCING AN ADDITIONAL AMOUNT OF THE THIRD COMPOUND IN THE REACTION ZONE AND TERMINIATING THE PROCESS WHEN THE REACTION MIXTURE CONTAINS THE THIRD COMPOUND IN AN AMOUNT GREATER THAN THE AMOUNT INITIALLY PRESENT.

3 Sheets-Sheet 1 N. L. CARR ET AL PROCESS FOR PREPARING A MONOALKYL AROMATIC Nov. 13, 1973 Filed Aug. us, 1971 lA/VEA/TORS. NORMA/V 4 04a 041x054 Y. c./(0

e/$97014 NOLLVb'JA/JJ/VOJ 3,772,398 Patented Nov. 13, 1973 3,772,398 PREPARING A MONOALKYL I j rnocnss'ron YAROMATIC "Norman L. can, Allison Park, andDaniel Y. 0. K0, Pitts- "burgh, Pa., assignors to Gulf Research & Developmen Company, Pittsburgh, Pa. Filed Aug. 13, 1971, Ser. No. 171,540

Int. Cl. C07c 3/52 U.S. Cl. 260671 P 12 Claims ABSTRACT OF THE DISCLOSURE the third compound is initially present in the reaction zone in an amount greater thanthe amount that would be present at equilibrium, which involves introducing an additional amount of the third compound in the reaction zone and terminating the process when the reaction mixture contains the third compound in an amount greater than the amount initially present.

This invention relates. to a process wherein there occurs essentially irreversible and equilibrium-limited reactions, illustrated, forexample, by the following general reaction mechanisms:

wherein ecah of M, N and O are chemical compounds.

In the above reactions, a reaction mixture containing compound M is converted, in any manner, batch or continuous operation, with or without catalyst, to compound N in an essentially irreversible reaction or said compound M is converted to said compound N and to compound in essentially irreversible reactions. Compounds N and 0, on the other hand, are convertible to ecah other in essentially equilibrium-limited reactions. During the course of the, reactions the concentration of said compound 0 reaches an amount in excess of that amount present at equilibrium before the reaction mixture reaches equilibrium. z r

In our copending application Ser. No. 171,541, entitled, Improvement in Irreversible and Equilibrium- Limited Reactions, filed concurrently herewith, we have found that in processes, such as defined above, we can minimize the formation of said compound 0 and, in fact,

.we can virtually eliminate net production of said compound O in' said process, as well as reduce the reaction time and still maintain desired conversions and selectivity to said compound N, by the mere expedient of adding said compoundO to the reaction zone in an amount greater than the amount that would be present at equi- -.-librium and terminating the process before the reaction mixture reaches equilibrium, preferably when the amount of said compound 0 is the reaction product corresponds substantially to the-amount of said compound 0 initially added to the reaction zone.

We further found in our copending application, referred to above, that the improvement was equally valid whether or not two or more reactants were employed resulting in the formation of two or more reaction products, for example, in the reaction of benzene (B) with propylene '(P), to produce a reaction product containing desired cumene (C) and undesired diisopropyl benzene (D):

We have now found that by introducing into the reaction zone an additional amount of said compound 0 (or D, for example, in a process such as illustrated immediately above), so that the resulting amount of said compound 0 is in excess of the amount initially added in our said copending application the residence time required to obtain the same conversion and yield to the desired compound, as in said copending application, is materially reduced, while at the same time production of said compound 0 is virtually eliminated, as in our said copending application.

The process of this invention can further be illustrated by reference to the following reaction mechanisms:

the kinetics of which are postulated as follows: r =k C r =k C r =k C and r =k C In the above, k k k and k, are reaction rate constants, r r r and r are reaction rates and C C and C are the concentrations of compounds M, N and 0, respectively, and are assumed to have a dimension of mols per cubic centimeter. A differential material balance was set up for each of compounds M, N and O and the resulting diiferential equations were programmed on an analog computer. The reactions were assumed to take place either in a flow reactor or in a batch reactor. In a flow reactor time is referred to as residence time and for a batch reactor the time was considered actual time or batch time. Using the values of k =0.0926, k =0.6l5, k =0.069 and k.,=0.64, the concentration profiles of compound 0 shown in FIG. I were obtained for compound 0. In FIG. I concentration in mols of compound 0 per cubic centimeter of reaction mixture is plotted against residence time or batch time in seconds. Consider the addition of 0.1 mol of compound C as being the amount normally added to the initial reaction mixture, as in our said copending application, necessary to obtain the desired results therein. When the reaction is terminated prior to equilibrium but when the amount of said compound 0 is equal to the amount initially present in the reaction mixture, a residence time of eight seconds is required. When runs are made wherein 0.2 or 0.3 mol of compound O are added to the initial reaction mixture, however, ..we obtain concentration profiles for compound 0 in the reaction product corresponding to the concentration profile obtained when 0.1 mol of said compound 0 is in the initial reaction mixture. Unexpectedly, we have found that when said reactions are similarly terminated prior to equilibrium and when the amount of said compound O in the reaction product is equal to the total amount (the amount initially present and the additional amount added therein) present at the beginning of the reaction, the residence time required to obtain the same selectivities to desired compound N, as in our said copending application, has been reduced to 4.2 and 3.15 seconds,

respectively.

consisting basically of an open,three-dimensioned'framework of SiO.; and A tetrahedra, having a silica to alu- V wherein y generally has a 'value of 0, but can vary from computer."Simulation studies were then conducite d to determine the rate constant and the associated activation I "energies so that the kinetic'model'representedthe' expe'ri mental data. Using the model so obtained simulated reactions were carried out on the computer wherein benzene was reacted with propylene to obtain cumene and diisopropyl'benzene. The first reaction was carried out using a benzene to propylene molar ratio of 6:1 and at emperature of 232 C. and thesecond a molar ratio of 4:1 and a temperature of 232 C. Concentration profiles for'diisopropyl benzene for these runs are shown in Figures II and III, respectively, wherein theconcentration of diisopropyl benzene in mols per'lO mols of total fluid are plotted against liquid weight hourly space time (LWHST) Note in each case when the amount of diisopropyl benzene In i Y isolitic in the initial reaction. mixture is in excess of the base f ar Sleve 0 t e O owmg umt cc ormu a was amount present (0.064 mol in Figure II and 0.155 mol in use Figure III) and the reaction is-terminated prior to equilib- (La+++) (NH+ (Na+) rium but when the amount of diisopropyl benzene in the [(A1O .,(SiO ]-ZH O reacttion mixtture etqitilals tliet tottalhamount thefieoi reac lOIl mix ure a e 1n e o t e reactor t e f 33? 31 2 3 giggt gg gg i g $25353 is drastically reduced. In each case there is virtually no loss of NH a H O therefrom oncPhalf inch inner net production of diisopropyl benzene and'hence 100 perdiameter 52-inch lo ng stainless reactor equipped with a Cent selectivity to cumene is achieved three-inch by 50-inch outer jacket filled with dixylylethane z i 2; i 2 g iziingfi g gi gi igi gg533 2:: as a heat transfer medium was used. Heat was su lied l with a calrod electrical heater and was controlled iiy a be i i with an olefin to g g alkyliammancb 9 examp e enzene can e reacte wit propy one to o tam thermoelectric controller. A thermowell extended coaxial- 1y through the reactor The temperature in the reactor cumene as the desired compound and dlISOPIOPYl benzene was measured by thermocouples evenly spaced through 30 gzg fi fz ff iggggag gg i 2 1 222L 5 i g the preheat section, catalyst bed and support section. The perature about to abou't C prcfrably about pressure was controlled by means of a pressure control to o about 235 C. and a pressure of about 350 to valve in the effluent line. Feed to the reactor was um (I upflow by an adjustable stroke proportioning puni p fr o m 388 mgjpounds per Square Inch gaugeiplreferably about a calibrated feed ank. The reactor was filled with a preg E pgunds per Square Inch gauge at heat section of glass beads to a depth of 14 inches. The 0 O4 to g i g igg g'g i ggfig zgfisggg 2:2 2 l i g g ggg gggfi f q that can be present at equilibrium can be from about 0.01

o lecular s1eve catalyst defined immediately hereinabove t fi g z rtnol 8 g g f i with two volumes of 8 to 10 mesh quartz per volume of m 1 n our the catalyst. The remaining reactor length was filled with copen. mg app Canon We ave t 6 amount glass beads. The eifiuent from the reactor was cooled and undesu'ed fompound added to Flmal reactlon collected in a gas-liquid separator. The off-gas was measture was excess of Such equlllbrlum amount o ured by a wet test meter, while the liquid product was 4? example, from about to about Preferably from recovered and weighed. The results obtained are tabu- 0 about one to about 0 P t m ar excess. In accordlated below in Table I. ance with the process defined and claimed herein we add TABLE I Run number 1 2 3 4 5 6 7 8 9 10 l gressurmtpoundi3 per square inch gauge. 3300 ggO i em era ure, 2 2 Benz ne to propylene, molar ratio 9. 96 9. 96 9. 96 9. 96 9. 96 9. 96 9. 96 5. 905 5. 905 5. 905 5 905 R HtSTt i 16b 0.0127 0. 0498 0.1054 0. 0129 0.02525 0.0506 0. 0833 0.01262 0.0267 0.0515 0.1

0 S mo S 8 ms I B I l ZeI16- l-.--%f j 1. 215 1. 215 1.215 1.215 1.215 1.215 1. 215 1.1733 1.1733 1.1733 1.1733 P gro ylen e 0.122 0.122 0.122 0.122 0.122 0.122 0.122 0.1986 0.1986 0.1096 0.1986

1.1027 1.10 1.09 1. 1 3.51%? M03; 1. .4 1322 .31% .34% 0.1038 0.111 0.1128 0.0 Di i s giii opylbenzenmfl 0.00813 0.00356 0. 00273 0.01133 0. 00849 0.00485 0.0310 0.0240 0.01223 0.00810 0.0073 Propylene 0. 0 0. 0. 0 0. 0 0. 0 0. 0 0. 0 0. 0- .0. 0 O. 0 0. 0

1 Liquid weight hourly space time=gram catalyst hour/grams of total fluid.

7 M01s/100 grams of total fluid, with total fluid including total reaction mixture.

Based on the above data the following reaction mechanism and kinetics were proposed:

1 Benzene (B) Propylene (P) Cumene (0) k2 Benezene 2 Propylene -v Diisopropyl Benzene (D) still an additional amount of undesired compound so that the mol percent thereof present inv the'initial reaction mixture is from about 0.2 to about percent, preferably from about two to about 60 percent, based on the total reaction mixture. As'in our said copendingapplication the process is preferably terminated prior to thetime the reaction product reaches equilibrium, most preferably when the amount of undesired compound in the reaction product is equal to the total amount in the reaction mixture at the inlet of the reactor. i

The improvement herein has been both broadly and specifically described and defined, but it is apparent that the same is applicable to any process wherein there occurs essentially irreversible and equilibrium-limited reactions, as exemplified by the general reaction mechanisms defined above, for example, alkylation reactions, such as the alkylation of benzene with propylene or ethylene to obtain cumene or ethyl benzene, respectively, as desired compounds and diisopropyl benzene or diethyl benzene, respectively, as undesired compounds, or the alkylation of toluene with propylene to obtain cumene as the desired compound and diisopropyl toluene as the undesired compound, dealkylation reactions, such as the reaction of toluene with hydrogen at elevated temperatures to obtain benzene as the desired compound and diphenyl as the undesired compound, etc.

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In a process wherein an olefin is converted, by reaction with an aromatic hydrocarbon, to a monoalkyl aromatic and to a dialkyl aromatic in essentially irreversible reactions, said monoalkyl aromatic and said dialkyl aromatic are convertible to each other in equilibriumlimited reactions and said dialkyl aromatic is initially present in the reaction zone in an amount greater than the amount that would be present at equilibrium, during the course of said reactions the concentration of said dialkyl aromatic reaches an amount in excess of that amount present at equilibrium before the reaction mixture reaches equilibrium, the improvement which comprises introducing an additional amount of said dialkyl aromatic in the reaction zone and terminating the reaction when the reaction mixture contains said dialkyl aromatic in an amount greater than the amount initially present.

2. The process of claim 1 wherein the amount of said dialkyl aromatic in the reaction product upon termination of the reaction corresponds substantially to the total amount of said dialkyl aromatic present at the beginning of the reaction. I

3. The process of claim 2 wherein said dialkyl aromatic in the reaction product is recycled to the reaction zone.

4. The process of claim 1 wherein said olefin is propylene, which is reacted with benzene to obtain cumene, diisopropyl benzene is said dialkyl aromatic and said diisopropyl benzene and cumene are convertible to each other in equilibrium-limited reactions.

5. The process of claim 4 wherein the amount of diisopropyl benzene upon termination of the reaction corresponds substantially to the total amount of diisopropyl benzene present at the inlet of the reactor.

6. The process of claim 5 wherein the diisopropyl benzene in the reaction product is recycled to the reaction zone.

7. The process of claim 1 wherein the total amount of said dialkyl aromatic in said reaction mixture is from about 0.2 to about 100 mol percent that would be present at equilibrium.

8. The process of claim 1 wherein the total amount of said dialkyl aromatic in said reaction mixture is from about two to about mol percent that would be present at equilibrium.

9. Theprocess of claim 4 wherein the total amount of said dialkyl aromatic in said reaction mixture is from about 0.2 to about mol percent that would be present at equilibrium.

10. The process of claim 5 wherein the total amount of said dialkyl aromatic in said reaction mixture is from about two to about 60 mol percent that would be present at equilibrium.

11. The process of claim 4 wherein the reactants are benzene and propylene and are present in a molar ratio of about 1:1 to about 15:1, the reaction temperature is about to about 260 C. and the pressure about 350 to about 700* pounds per square inch gauge.

12. The process of claim 4 wherein the reactants are benzene and propylene and are present in a molar ratio of about 5:1 to about 10:1, the reaction temperature is about 200 to about 235 C. and the pressure about 400 to about 550 pounds per square inch gauge.

References Cited UNITED STATES PATENTS 2,403,785 7/1946 Britton et a1. 260-671 R 2,818,452 12/1957 Mavity 260-671 P 2,995,611 8/1961 Linn et a1. 260-671 R 2,883,438 4/1959 Egbert 260-671 P 2,920,118 1/1960 Landau et al 260-671 P 3,274,278 9/1966 Kapur et a1 260-671 B 3,385,906 5/1968 Kaufman 260-671 P OTHER REFERENCES Hougen et al.: Chemical Process Principles, Pt. II, 2d Edition, John Wiley & Sons, New York (1954) pp. 1020-1.

CURTIS R. DAVIS, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 772,398 Dated November 13, 1973 Inventofls) Norman L. Carr and Daniel Y. C. Ko

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 52, "171,541" should be "171,474".

Column 3, line 335,, "sank" should be "tank".

Column 4, last column of Table 1, Run No. "1'' should be *"lllk, v

4 under Run No. 10 of Table I, 0.1996" elwuld be 0.198%H Signed and sealed this 23rd day of April 1 9714.,

MEAL) Aime 5:

REWARD BT IIFLETGHERJ'H Y C MARSHALL DANN Atte Cffioer flommissloner of Patents 

